1. Field of the Invention
The present invention relates to heat transfer and more particularly to the method and apparatus used to heat the fuel for a diesel internal combustion engine to prevent fuel system blockage in cold weather due to crystalization in, or separation of wax from, the fuel.
2. Description of Related Art
Characterizing the closest prior art of which the applicant is aware and in compliance with 37 C.F.R. S 1.97 and S 1.98 attention is invited to the following U.S. Pat. Nos.
Bennett: 493,855; Mar. 21, 1893 PA1 Knaak: 1,107,967; Aug. 18, 1914 PA1 Dixon: 1,148,892; Aug. 3, 1915 PA1 Robinson: 2,680,692; June 8, 1954 PA1 Gendron: 4,364,365; Dec. 21, 1982 PA1 Leibrand: 4,326,492; Apr. 27, 1982 PA1 Reinhard: 4,454,841; June 19, 1984
The Bennet U.S. Pat. No. 493,855 is believed relevant in its disclosure of fire brick as a heat transfer medium.
The Knaak U.S. Pat. No. 1,107,967 is believed relevant in its disclosure of asbestos as a heat retaining medium.
The Dixon U.S. Pat. No. 1,148,892 is believed relevant in its disclosure of metallic particles as a heat transfer medium.
The Robinson U.S. Pat. No. 2,680,692 is believed relevant in its disclosure of stabilized alumina heat exchange pellets as a heat transfer medium.
The Gendron U.S. Pat. No. 4,364,365 is believed relevant in its disclosure of charcoal as a heat transfer medium.
The Leibrand U.S. Pat. No. 4,326,492 is believed relevant in its disclosure of oil as a heat transfer medium.
The Reinhard U.S. Pat. No. 4,454,841 is believed relevant in its disclosure of metallic particles as a heat transfer medium.
Diesel fuel must be maintained above approximately 60 degrees F. (15.6 C.) to prevent wax formation. It is also necessary to prevent the temperature from rising substantially above 100 degrees F. (37.7 C.) to prevent deterioration of the fuel.
The use of a heat exchanger to transfer heat from the engine exhaust is well known. Prior art devices have used a coil of metallic tubing wound tightly around the exhaust conduit through which the exhaust gasses flow or by spacing the coil at some distance and using a heat transfer medium such as air, oil, charcoal, alumina, metal foils or particles, to transfer the heat to the fuel coil.
A recent patent teaches the use of oil as a heat transfer medium. Apparatus based upon this patent have been produced and marketed. The apparatus has been effective in raising the fuel temperature to an acceptable degree but heat transfer at the higher temperatures is sometimes excessive. A serious threat has developed due to oil leaking from the apparatus for fire damage. The plurality of tube fastenings coupled with seam failure in the container in an environment of thermal shock and mechanical vibation are major contibutors to oil leakage.